The field of the invention is that of pressure responsive devices, and the invention relates more particularly to a temperature compensated device responsive to change in pressure in a pressure system indicative of a loss of gas from the system at any temperature within a selected temperature range.
Conventional pressure responsive devices arrange a diaphragm to move in response to an applied fluid pressure to actuate a control to provide a signal or perform a related function corresponding to the level of the applied pressure. In a typical device, movement of the diaphragm is normally opposed by a spring which calibrates the device to provide the desired control signal when the applied fluid pressure is at a selected level. Sometimes the diaphragm itself or a member of the control is provided with selected resilience which cooperates with the spring to actuate the control when the applied pressure is at the actuating level. Frequently, however, it is difficult or impossible to calibrate such pressure responsive devices to provide the desired control signal at a precisely predetermined pressure level, and this is particularly true where portions of the applied fluid pressure are attributable to different causes or are subject to different calibration requirements. For example, where a pressure responsive device is intended to sense a loss of gas from a pressure system but where the gas pressure in the system varies with temperature in accordance with the ideal gas law for example, it has not previously been possible to detect the loss of gas from the system with any suitable degree of accuracy. Similarly, where a pressure responsive device is intended to withstand very high pressure levels while also being responsive to small changes in applied pressure, it has been difficult to provide a suitably compact device which meets both high pressure and accurate calibration or pressure sensing requirements.